What absorbs at 3445 cm⁻¹ in an FTIR spectrum?
A band near 3445 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Quick answer
A band near 3445 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Hydroxyl (O-H) | 22 | 22 | 1.0 |
| Water (H2O) | 9 | 8 | 1.0 |
| N h | 8 | 8 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Silanol (Si-OH) | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| graphene | 3445, 1720, 2097 | Hydroxyl (O-H) | 3 |
| CA | 3445, 1045, 1650 | Hydroxyl (O-H) | 1 |
| asphalt | 3445, 1600, 1376 | Hydroxyl (O-H) | 1 |
Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.
Spectrum logic
This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 3445 cm⁻¹ is usually not enough for material identification by itself.
Real-world usage
This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.
Common mistakes
- Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
- Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
- Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.
Verification advice
When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.
Literature behind these assignments
-
Hydroxyl (O-H) confidence 1.0
“As it can be seen, the samples exhibit an absorption peak at ¹ and broad band around 3445 c ¹, corresponding to H-O-H bending and free OH stretching vibration.”
Modified structural and magnetic properties of nanocrystalline MnFe2O4 by pH in capping agent free co-precipitation method DOI: 10.1016/j.jmmm.2016.10.105 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Khanra 等 - 2014 - 7,7,8,8-Tetracyanoquinodimethane-assisted one-step DOI: 10.1039/c3nr05307e -
N-O bond confidence 1.0
“cm-1, cm-1, 3200 the negative influence of PC1 loadings had one peak at 3445 whereas the positive influence of PC1 had no peak.”
Specific Mycoparasite-Fusarium Graminearum Molecular Signatures in Germinating Seeds Disabled Fusarium Head Blight Pathogen’s Infection DOI: 10.3390/ijms22052461 -
Hydroxyl (O-H) confidence 1.0
“that the peak at 3445 belongs to -OH groups vibrations in water molecules, located near TGA molecules and promoting the H-bond bridges formation, including dimerization process.”
Kondratenko 等 - 2020 - Thioglycolic Acid FTIR Spectra on Ag2S Quantum Dot DOI: 10.3390/ma13040909 -
Hydroxyl (O-H) confidence 1.0
“Finally, the strong and wide cm(cid:3)1 OAH absorption peak at 3445 is attributed to the stretching”
Properties and modification mechanism of asphalt with graphene as modifier DOI: 10.1016/j.conbuildmat.2020.121919 -
Hydroxyl (O-H) confidence 1.0
“FTIR spectra after immersion for prolonged times either before and after gamma cm-1 irradiation show formation of characteristic two far-IR peaks at about 730 and 550 together cm-1 with the formation or increase in the intensity of the peak”
Okasha 等 - 2020 - Bone bonding augmentation and synergetic attitude DOI: 10.1016/j.radphyschem.2020.109018 -
Hydroxyl (O-H) confidence 1.0
“in ionic conductivity is attributed to the increase in the ment O-H stretching 3445 CA concentration of amorphous phase upon the disruption of bonding stretching (CH3) 2932 C-H”
Plasticizing effect of 1-allyl-3-methylimidazolium chloride in cellulose acetate based polymer electrolytes DOI: 10.1016/j.carbpol.2011.11.037 -
Hydroxyl (O-H) confidence 1.0
“4 reveals several peaks, for cm-1 instance, the peak at 3445 as the broadest peak with high intensity supposedly correspond to hydroxyl (-OH)”
Synthesis and characterization of carbonaceous-based nanomaterials produced in chemical vapor deposition (CVD) using copper catalyst DOI: 10.1063/5.0005445
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